Television receiving system



Sept. 14, 1937. T. NAKASHIMA El AL TELEVISION RECEIVING SYSTEM FiledAug. 1, 1933 INV EN TORfi. W I 'I l I f f] 1 I BY A TTORNEYS PatentedSept. 14, 1937 TELEVISION RECEIVING SYSTEM Tomomasa Nakashima andKenjiro Takayanagi,

Hamarnatsu, Japan W Application August 1, 1933, Serial No. scans InJapan December 12. 1932 4 Claims. (oi. 178-6) This invention relates totelevision receiving systems and more particularly to televisionscanning systems whereby the pictures are produced on the fluorescentscreen of a Braun tube by series of distinct spots without trace ofscanning lines, and its principal object is to provide very fine andclear television pictures by simple and reliable means.

In television systems using a cathode ray tube, such as a Braun tube, atthe television receiving end, pretty good results may be obtained withthe deflecting current or voltage, especially the current or voltage ofa saw tooth wave form applied to the deflecting coil or plate providedfor the Braun tube in synchronism and in the same phase with respect tothe scanning operation at the sending station. In former systems,however, all picture elements on the fluorescent screen are connected bythe scanning motion and the image consists of parallel scanning lines sothat the observer feels disagreeable.

In accordance with this invention the above defects owing to thecontinuation of the seaming lines is obviated by producing each pictureelement by a series of distinct and independent spots.

For the consideration of what we believe to be novel and our invention,attention is directed to the following specification and the claimsappended thereto. In the drawing, Fig. 1 is a connection diagramillustrating a television receiving system embodying this invention;Fig. 2 shows curves taken for explanation of this invention; Figs. 3 and4 are connection diagrams illustrating modified arrangements of thisinvention.

Referring to Fig. 1 of the drawing, I represents a low frequencyoscillator of an ordinary type having the frequency equal to the numberof pietures per second. 2 is a saw tooth current generating means whichis controlled by the oscillator l and which produces a. saw tooth shapedcurrent of the same frequency as that of the low frequency oscillator l.The output side of the saw tooth shaped current generator 2 is connectedto one set of deflecting coils 4 of a Braun tube 3 to effect low speedscanning operation. The Braun tube 3 for simplicity should naturally beconnected and arranged in an ordinary manner for television systems,though the picture current receiving system is not shown in the drawing.However, 5 represents an oscillator having the frequency equal to theline scanning frequency, and B is a saw tooth wave form currentgenerating means having the same frequency as that of the oscillator 5.The output side of the saw tooth current generator 6 is connected to theother set of deflecting coils I which are arranged at right angle withrespect to the deflecting coils 4 to effect the line scanning operation.In the above arrangement, the oscillators l and 5 should of course beoperated in synchronism with the scanning operation in the sendingstation. In other words, a picture current receiving circuit should beassociated with the grid of the Braun tube 3 in order to control thecathode ray corresponding to the luminous variation of the pictureelements.

With the arrangement so far explained in the above which is an ordinaryarrangement of deflecting coils, the fluorescent screen 8 of the Brauntube 3 will be scanned only once for each picture at substantiallyuniform scanning speed by the cathode ray controlled by the deflectingcoils 4 and I. Such condition can be explained more clearly by Fig. 2.In Fig. 2--A, the line 9 represents the direction of scanning cathoderay and I0 represents a spot corresponding to a picture element.Residual light or trace of the scanning line is left in the space 9'between the spots so that the entire picture will become indistinct.

In accordance with this invention, (refer to Fig. 1) an auxiliarydeflecting coil L is wound differentially with respect to the high speedscanning deflecting coil 1, and arranged in close relation thereto. Theauxiliary coil is connected in the output circuit of an oscillator llhaving the frequency equal about to the number of picture elements persecond. The oscillator II should be operated in the same phase relationwith the oscillators i and 5 by starting them simultaneously. Though theoscillator ll may be of any suitable type which produces a voltage orcurrent of any suitable wave form, yet such an oscillator whichgenerates a voltage of sine wave form or the like is illustrated in thedrawing. i 2 designates an oscillator valve and I3 is an oscillationelement consisting of a condenser and an inductance, connected in thegrid circuit of the oscillator valve l2. l4 shows an oscillationcoupling coil which is connected to the plate circuit of the oscillatorwave l2 and cooperates with the oscillation element l3. I5 is a gridbias device such as consisting of a capacity and a resistance, while l6and I! represent the A- and B-batteries of the oscillator valve l2respectively. The coupling coil L is preferably energized through a sawtooth shaped current generating means II which is controlled by theoscillator II with the current or voltage of saw tooth wave form havingthe frequency equal to the number of the picture elements to be producedper second.

The operation of the above mentioned arrangement is as followsz-Assumingthat the device shown in Fig. 1 is operated in synchronism with thescanning operations at the sending station, and so that the cathode rayin the Braun tube 3 is controlled by the grid thereof in a mannercorresponding to the luminous variation of the picture elements, thenthe magnetic field caused by one-half cycle of the current passingthrough the deflecting coil L will oppose, at the position correspondingto every picture element, to the magnetic field caused by the currentpassing through the high speed scanning deflecting coil I so that thedeflection of the cathode ray may be momentarily stopped or tend todecelerate at the position corresponding to every picture element asshown by 88 in Fig. 2-3. Then the cathode ray will be quickly shifted tothe next spot since at the position between adjacent picture elementsthe cathode ray is accelerated by the resultant magnetic field caused bythe cooperation of currents passing through the main deflecting coil 8and the auxiliary deflecting coil L so that the scanning line can not beseen clearly-as shown by id in Fig. 2-3. By properly regulating theintensity of current supplied to the deflecting coil L more distinctpicture elements i9 may be produced and clear images may be seen withoutinfluence of the scanning lines. The intensity of the current suppliedto the deflecting coil L is such that the cathode ray is deflected backonly for a very short distance equal to the size of one picture elementat the position corresponding to every picture element, in the directionopposite to the normal scanning direction of the cathode ray due to thecurrent passing through the deflecting coil 5, so that a very smallcurrent through the deflecting coil L is enough for this purpose. If thedeflecting coil L is arranged in oblique relation to the deflecting coilI the picture element will be produced obliquely to the direction of thescanning line and then the trace of the scanning line may be eliminatedmore efl'ectively.

In Fig. 3, instead of the deflecting coil L, a pair of oppositedeflecting plates 20 is arranged at the position parallel to the fieldof the deflecting coil L and applied with the output voltage of theoscillator H. The other connections are similar to those described withreference to Fig. 1. In this arrangement, the cathode ray will bedeflected in the direction of the electric field which is produced bythe deflecting plates 20 and which is normal to the magnetic fieldcaused by the deflecting coil I so that the object of this invention mayequally be attained with the same result as explained with regard toFig. 1, if the polarities of the deflecting plates 20 are properlyselected.

In the modified arrangement of this invention shown in Fig. 4, theoscillator ll having the frequency equal to the number of pictureelements per second is connected to the primary winding of a transformer22, the secondary winding of which is inserted in the grid or platecircuit of an amplifying vacuum valve 2| which is connected to the sawtooth voltage or current generating means 6 of the high speed scanningfrequency. Thus the auxiliary deflecting coil L in Fig. l or plates 20in Fig. 3 can be omitted. 23 and 2d are the grid bias resistance andgrid bias source of the amplifying valve 25 respectively. 25 and 26represent the A- and B-batteries respectively.

In this arrangement, the deflecting voltage of the line scanningfrequency applied from the saw tooth wave form voltage generating meansand the voltage having the frequency equal to the number of pictureelements applied from the oscillator H are superposed in the deflectingcoil l. Hence the cathode ray may be deflected in the manner similar tothat described above so as to produce the distinct picture elements.

Assume, for instance, that one picture consists of 10,000 pictureelements and that the number of pictures interchanged per second istwenty, then the number of picture elements per second will become200,000. The object of this invention will be attained by selecting thenumber of frequencies oi the oscillators or generators l, 5 and H as 20,2,000 and 200,000 respectively and by operating these oscillators in thesame phase as those of the sending station. 7

'As above described according to this invention, the picture elementscan be seerf as the distinct spots free from the trace of scanning linesso that the image can be seen very clearly on the fluorescent screen ofthe Braun tube.

What we claim as new and desire to secure by Letters Patent of theUnited States, is:

1. In television receiving systems using a cathode ray tube having acontrol grid. the combination of an electro-magnetic coil arranged ad-Jacent to the cathode ray tube to deflect the grid controlled cathoderay in such cathode ray tube at a frequency equal to the number ofpictures per second, an electro-magnetic coil arranged normally to saidfirst mentioned electro-magnetic coil and adjacent to the cathode raytube for deflecting the grid controlled cathode ray at the line scanningfrequency, 'an auxiliary deflecting coil wound diiferentially andarranged closely to said electromagnetic coil for the line scanningfrequency speed to accelerate and decelerate the line scanning speed ofthe grid controlled cathode ray in the direction of the line scanning ata frequency equal to the number of the picture elements per second, saidelectromagnetic coils being energized. respectively, from an oscillatorhaving a frequency equal to the number of pictures per second, anoscillator having the line scanning frequency and an oscillator forgenerating 2. current of any wave form having a frequency equal to thenumber of picture elements per second for energizing said auxiliarydeflecting coil, and thereby decelerating the line scanning speed of thegrid controlled cathode ray against the deflecting action of said secondmentioned electromagnetic coil so as to stop the grid controlled cathoderay at a position corresponding to every picture element.

2. In television receiving systems using a cathode ray tube having acontrol grid, the combination of an electromagnetic coil arranged adiacent to the cathode ray tube to deflect the grid controlled cathode rayat a frequency equal to the number of pictures per second, anelectromagnetic coil arranged normally to said first mentionedelectromagnetic coil and adjacent to said cathode ray tube to deflectthe grid controlled cathode ray at the line scanning frequency, anauxiliary deflecting plate arranged normally to said second mentionedelectromagnetic coil and closely to said cathode ray tube to accelerateand decelerate the line scanning speed of the grid controlled cathoderay in the direction of line scanning at a frequency equal to the numberof the picture elements per second, said electromagnetic coils beingenergized, respectively, from an oscillator having a frequency equal tothe number of pictures per second, an oscillator having the linescanning frequency and an oscillator for generating the voltage of afrequency equal to thenumber of picture elements per second to beapplied to said auxiliary deflecting plate, and thereby decelerating theline scanning speed of the grid controlled cathode ray in opposition tothe deflecting action of said second mentioned electromagnetic coil soas to stop the grid controlled cathode ray at a position of everypicture element.

3. In a television image producing system using a Braun tube having acontrol grid, the combination of an electromagnetic coil arranged ad--jacent to said Braun tube for deflecting the grid controlled cathode rayin said Braun tube ,1

at a frequency equal to the number of pictures per second, anelectromagnetic coil arranged normally to said electromagnetic coil andadjacent to said Braun tube to deflect the grid controlled cathode rayin said Braun tube at the line scanning frequency, a saw tooth wave formcurrent generator controlled by an oscillator having a frequency equalto the number of pictures per second for energizing said first mentionedelectromagnetic coil, another saw tooth wave form current generatorcontrolled by an oscillator having the line scanning frequency forenergizing said second mentioned electromagnetic coil, an amplifyingvacuum valve, the input circuit of which is connected to said secondmentioned saw tooth wave form current generator and the output circuitof which is connected to said second mentioned electromagnetic coil, andan oscillator of a frequency equal to the number of the picture elementsper second connected in the grid circuit of said amplifying vacuum valveto energize said second mentioned electromagnetic coil through saidamplifying vacuum valve in such a manner that the line scanning speed ofthe grid controlled cathode ray in said Braun tube is decelerated so asto stop the grid controlled cathode ray at the position corresponding tothe picture elements and accelerated in the space between the adjacentpicture elements.

4. In a television receiving system utilizing a cathode ray tube havinga constant grid which controls the cathode ray corresponding to thebrightness of the picture elements, the combination of means fordeflecting said grid controlled cathode ray in said cathode ray tube ata frequency equal to the number of pictures per second, means also fordeflecting said cathode ray within said tube in a direction normal tothe first deflecting means at the line-scanning frequency, auxiliarymeans for accelerating and decelerating the line scanning frequency ofsaid grid controlled cathode ray in the direction of the line scanningat a frequency equal to the number of picture elements per second, saidmeans being energized, respectively, from an oscillator having afrequency equal to the number of pictures per second, an oscillatorhaving the line scanning frequency and an oscillator for generating acurrent of any wave form having a frequency equal to the number ofpicture elementsper second to be applied to said auxiliary means, andthereby decelerating the line scanning speed of the grid controlledcathode ray in opposition to the deflecting action of said seconddeflecting means so as to momentarily stop said grid controlled cathoderay at a position corresponding to every picture element.

TOMOMASA NAKASHIMA. KENJIRO TAKAYANAGI.

